Autoimmune diseases are pathological conditions where an immune response is triggered by tissues and substances naturally present in the body. This unwanted and inappropriate immune reaction can be tissue-specific, organ-specific or systemic. The course of the disease proceeds from mild symptoms to irreversible destruction of specific tissues and/or organs.
Rheumatoid arthritis is a heterogeneous and partially genetically determined inflammatory disease, where autoimmunity is assumed to play an important pathogenic role, but where the specificity of the autoimmune reactions and the genetic determinants of these reactions remains incompletely known. It is a chronic and incurable disease that causes irreversible damage to the articular cartilage and bone, and which leads to progressive physical disability,
The treatment and/or alleviation of rheumatoid arthritis, as well as other inflammatory and autoimmune diseases, have so far been based on the manipulation of immune and inflammatory events without knowing the detailed immunological basis of the disease. These therapies include traditional disease-modifying anti-rheumatic therapies (DMARD:s), including the administration of drugs such as methotrexate, sulfasalazine, azathioprine, leflunomide, hydroxychloroquine and cyclosporine. Methotrexate is often considered as the first choice medication. This drug is, however, associated with both milder and reversible side-effects, such as gastrointestinal and oral mucosal ulceration, but also with more serious, irreversible side effects, such as hepatic toxicity.
In addition to the DMARD:s, there are new protein-based therapies that affect cytokine regulation or broad aspects of T and B cell activation and migration. Examples are several monoclonal antibodies and a receptor construct that blocks TNF alpha, cytokine-blocking agents, such as antibodies against IL-6 receptor (tocilizumab), as well as therapies such as CTLA4Ig (abatacept) and anti-CD20 antibodies (rituximab) that influences entire classes of lymphocytes. Many novel therapies are not based on detailed knowledge of specificity of the autoimmune reactions in rheumatoid arthritis, but affect general signaling pathways. One such therapy is the Jak-2 inhibitor tofacitinib, currently in advanced clinical development. However, these novel therapeutics does still not address the specific autoimmune reaction but are non-specific treatments that affect large downstream parts of the immune and inflammation defense system, thereby giving rise to risks for side effects caused by a generally suppressed immune defense. Such side effects include sensitivity to infections and reduced response to vaccination.
Autoimmune reactions to certain epitopes of self antigens most likely contribute to the development of autoimmune diseases, such as rheumatoid arthritis. Antibodies against the patient's own proteins, in particular against native and/or post-translationally modified variants of certain proteins have been identified in patients with rheumatoid arthritis. Autoantibodies have been identified against collagen type II (the major protein in joint cartilage), alpha-enolase (an enzyme involved in glycolysis) and vimentin (an intermediate filament protein).
These antibodies are often—but not always—directed towards citrullinated variants of the proteins. Citrulline is an unconventional amino acid that results from the deimination of arginine. Citrullination of the arginine residue is a post-translational modification catalyzed by enzymes called peptidylarginine deiminases (PADs).
Previously, the use of citrullinated peptides as a diagnostic tool for rheumatoid arthritis (anti CCP) has been described (WO2003/050542). The CCP antibody assay uses a mixture of peptides that have not been demonstrated to occur as natural autoantigens (targets of B cells) in patients with rheumatoid arthritis.
Another reference, WO 2007/017556, describes the use of certain citrullinated and non-citrinullated peptides from collagen type II for the diagnosis of rheumatoid arthritis. Furthermore, the detection of a citrullinated enolase peptide (cep1) has been described as a diagnostic tool in rheumatoid arthritis (WO2008/090360). Citrullinated peptides from the protein vimentin have also been suggested for the diagnosis of rheumatoid arthritis (WO2007/123976).
However, these methods for diagnosis do not provide the whole picture of the disease in the individual since additional target molecules and mechanisms may be of importance for rheumatoid arthritis.
The available methods for diagnosis and treatment of autoimmune diseases clearly leave room for improvement. There is a need for a deeper insight into the pathogenesis of autoimmune diseases, as well as for the development of new diagnostic and therapeutic methods. With particular regard to rheumatoid arthritis, there is major unmet medical need for improved diagnosis and treatment. One problem in defining rheumatoid arthritis and its subsets has been the lack of a distinct clinical, laboratory or radiological marker for the disease and its subsets. Another problem resides in finding a reliable approach to both short-term and long-term monitoring of the progression or remission of the disease. A further problem resides in finding more specific and effective treatments, minimizing the side effects usually associated with both DMARD:s and currently available and currently developing therapies. These problems, and others evident to a skilled person upon study of the present description, will be addressed below.
Definitions
As used herein:
“Diagnosis”: refers to determining with respect to an individual: whether the individual has a disease or not and/or how severe the disease of the individual is and/or prognosis of the disease of the individual and/or expected response to treatment of the individual and/or or risk of developing the disease, classification of the disease, monitoring the progression of the disease or the results of intervention.
“Patient” refers to an individual that have a disease or that have an increased risk of developing a disease. Thus, the disease may not necessarily have presented in the individual for the individual to be considered to be a patient. The increased risk can be detected by, for example, determining the genotype of the patient.
“Variant” of a peptide refers to a variant of a defined peptide comprising from between 8 and 20 amino acids, more preferably of between 9 and 19, even more preferably of between 13 and 18 amino acids and most preferably between 14 and 16 amino acids, comprising at least 8 consecutive amino acids, more preferably at least 10 consecutive amino acids, more preferably at least 12 consecutive amino acids, more preferably at least 13 consecutive amino acids, more preferably 14 consecutive amino acids is present in the defined peptide. The remaining residues of the peptide, if any, can be any naturally occurring amino acid.
“Sample” when used in relation to cells, refers to the original cells and also to the descendants of those cells, as cells may proliferate during in vitro culture.
“Enolase”, as used herein, refers to the human alpha enolase protein.
“Amino acid”, when used in the context of a peptide or a protein, refers to amino acid residue.
The immune response is controlled by T-cells where activating T-cells such as effector T-cells enhance the immune response and regulatory T-cells constitute one of several mechanisms that inhibit the immune response. Thus, autoimmune disease is controlled by a balance of stimulating effector T-cells and regulatory T-cells. Effector T-cells and regulatory T-cells both belong to the class of T-helper cells. Activated effector T-cells secrete various pro-inflammatory cytokines such as interferon gamma, TNF alpha and IL-17 that contributes to inflammation.
The human leukocyte antigen (HLA) loci encodes the genes for human MHC class II proteins (referred to herein as “MHC” or “MHC protein”), which plays a crucial role in regulation of the immune system. Display of immunogenic peptides by MHC class II molecules on the surface of antigen-presenting cells serve as signals to T-cells which in turn control the immune reaction and also progression of the autoimmune disease by inducing proliferation of B-cells and production of pathological antibodies. A crucial step of T-cell activation is the binding of the T-cell receptor of the T-cell to a complex consisting of an antigenic peptide bound to the cleft of a MHC class II protein molecule on the surface of an antigen-presenting cell.
The MHC protein system is adapted to bind and exhibit diverse peptides to T-cells. This is usually beneficial since many different peptides, for example from pathogens, thereby can be detected by the immune system.
HLA genotypes are well known and have been described previously. The beta-subunit of the MHC protein is the subunit that contributes most to the diversity of MHC. In fact, the HLA-DRB1 locus on chromosome 6 that encodes this subunit is among the most diverse in man. Most differences are located in the peptide-binding cleft of the MHC protein.